The assumption the projection rests on
Electricity you consume as it is generated displaces a purchase at the retail rate, which averaged about 17.9 cents per kWh in Indiana in April 2026. Electricity you export earns the Excess Distributed Generation credit.
That credit is the prior year average wholesale cost plus 25 percent, which has run roughly 70 to 80 percent below retail. So a self-consumed kilowatt hour is worth several times an exported one.
It follows that two identical systems on identical roofs can produce very different savings depending only on when each household happens to use power.
The self-consumption share is therefore not a modelling detail. It is the assumption that determines the answer, and it should appear on the page rather than sitting inside a spreadsheet.
What share is realistic for your household
A household with someone home during the day, or with large daytime cooling load through an Indiana summer, consumes a high share of its generation directly. That is the favourable case.
A household that leaves at eight and returns at six, with the heaviest usage in the evening, exports most of its midday production at the low rate. The same roof and the same panels return substantially less.
Ask what self-consumption share the model assumed and what it was based on. An assumption drawn from your actual interval data, where your meter provides it, is far stronger than a generic figure.
Ask to see the projection at a lower share as well. If the case only works at an optimistic assumption about when you use power, that is worth knowing before you sign rather than discovering from bills.
Raising the share, free and paid
The free version is load shifting. Dishwasher, washing machine, dryer and pool pump all move easily into daylight, and each moved kilowatt hour is upgraded from the Excess Distributed Generation rate to the full retail rate.
Pre-cooling on a hot afternoon is usually the biggest free lever, because air conditioning is the largest load in the house and it can be run harder while the sun is up.
Charging an electric vehicle during the day rather than overnight is the single largest shift available to a household that has one.
The paid version is a battery, which does the same thing automatically and at scale. Under Indiana rules the gap it monetises is wide, so ask for the system modelled with and without storage so the incremental value appears as its own number.
Building the number from what Indiana still offers
The 30 percent federal Residential Clean Energy Credit under Section 25D expired for property placed in service after December 31, 2025, so a cash or loan purchase in Fishers receives no federal tax credit, and Indiana has no state income tax credit for solar.
Section 48E survives at 30 percent for third-party owners under leases and power purchase agreements, so ask what a provider claims and what reaches you in the rate.
What exists is the 7 percent sales tax exemption, the property tax exemption on added value, retail value for self-consumed generation, and the Excess Distributed Generation credit for exports.
Ask for the assumed self-consumption share stated, the projection shown at a lower share, and a smaller system modelled alongside the proposal.